docs: def _get_stddevs(self, coeffs, stddev_types, num_sites):
          """
          Return total sigma as reported in Table 2, p. 1202.
          """
          stddevs = []
          for stddev_type in stddev_types:
              assert stddev_type in self.DEFINED_FOR_STANDARD_DEVIATION_TYPES
              stddevs.append(coeffs['sigma'] + np.zeros(num_sites))
          return np.array(stddevs)